1. Field of the Invention
This invention relates to photothermographic elements, compositions and processes for providing a developed image in color. One of its aspects relates to photothermographic elements for providing such a developed image in color comprising photographic silver halide in association with a silver salt of a long-chain fatty acid and certain reducing agents which are oxidizable imagewise to provide the color image. In another of its aspects, it relates to photosensitive compositions for providing such a developed image in color containing the described components. A further aspect relates to a process of obtaining an image in color in an exposed photothermographic element containing the described components by uniformly heating the element.
2. Description of the State of the Art
It is well known to develop a latent image in a photothermographic element using processing with heat. After imagewise exposure, the resulting latent image in the photothermographic element is developed and, in some cases, stabilized, merely by uniformly heating the photothermographic element. Such materials and process are described, for example, in U.S. Pat. No. 3,152,904 of Sorensen et al., issued Oct. 13, 1964; U.S. Pat. No. 3,301,678 of Humphlett et al., issued Jan. 31, 1967; U.S. Pat. No. 3,392,020 of Yutzy et al., issued July 9, 1968; U.S. Pat. No. 3,457,075 of Morgan et al., issued July 22, 1969; British Patent No. 1,131,108 published Oct. 23, 1968; German Patent No. 888,045 issued June 29, 1943 and British Patent No. 1,161,777 published Aug. 20, 1969.
Certain photothermographic materials for producing a developed image in color are also known as described, for example, in U.S. Pat. No. 3,531,286 of Renfrew, issued Sept. 29, 1970 and U.S. Pat. No. 3,761,270 of deMauriac and Landholm, issued Sept. 25, 1973. The reducing agent employed in the materials of U.S. Pat. No. 3,531,286 of Renfrew employ paraphenylenediamine which can be unsuitably toxic. When the paraphenylenediamine is replaced with a less toxic reducing agent, such as an aminophenol, no suitable color image is developed. In the photothermographic materials of deMauriac and Landholm, a base-release agent is needed to provide the necessary color-forming reaction in the photothermographic material. In addition, a color-forming coupler is required in the described photothermographic materials. No suitable solution to elimination of these problems is evident from the described patents.
Thermographic materials are also known for providing an image in color. However, the image is provided by imagewise heating. Such thermographic materials are described, for example, in U.S. Pat. No. 3,094,417 of Workman, issued June 18, 1963 and U.S. Pat. No. 3,592,650 of De Selms, issued July 13, 1971. There are not useful for photographic processes requiring the photographic speed of photosensitive silver halide in which a latent image is provided by imagewise exposure to light.
Accordingly, there has been a continuing need for improved photothermographic materials for providing a developed image in color which also provide desired photosensitivity, eliminate the need for a separate color-forming coupler and can provide different colors such as cyan, magenta and yellow.